The invention relates to composite materials comprising film-forming hydrophilic colloids and ceramic nanoparticle materials.
For most types of gelatin-based imaging elements, surface abrasion and scratching results in reduction of image quality. For example, silver halide photographic elements contain light sensitive silver halide in a hydrophilic emulsion. An image is formed in the element by exposing the silver halide to light, or to other actinic radiation, and developing the exposed silver halide to reduce into elemental silver. In color photographic elements a dye image is formed as a consequence of silver halide development by one of several different processes. The most common is to allow a by-product of silver halide development, oxidized silver halide developing agent, to react with a dye forming compound called a coupler. The silver and unreacted silver halide are then removed from the photographic element, leaving a dye image. In either case, formation of the image commonly involves liquid processing with aqueous solutions that must penetrate the surface of the element to come into contact with silver halide and coupler. Thus, gelatin, and similar natural or synthetic hydrophilic polymers, have proven to be the binders of choice for silver halide photographic elements. Unfortunately, formulation of gelatin and similar polymers so as to facilitate contact between the silver halide crystal and aqueous processing solutions may lead to a final product lacking in toughness and especially, in scratch resistance. Thus, processing the image and, later, casual handling of the same, can easily mark or disfigure the image. There is, therefore, a need for an imaging element having improved scratch resistance over materials currently used.
It has been unexpectedly discovered that incorporation of a ceramic nanoparticle material, along with a film-forming hydrophilic colloid, in a layer of an imaging element subject to abrasion can dramatically improve the scratch resistance of the imaging element, while maintaining optical clarity. Accordingly, in one aspect, the present invention relates to nanocomposite materials comprising at least one film-forming hydrophilic colloid and at least one ceramic nanoparticle material. The film-forming hydrophilic colloid may be a gelatin, and the ceramic nanoparticle material may be alumina. In another aspect, the invention relates to scratch-resistant imaging elements comprising a support and a layer comprising such a nanocomposite material. The nanocomposite layer may be employed as an imaging layer, or as a protective layer disposed between an imaging layer and the environment.